Interconnection damping assignment passivity based control (IDA-PBC) is an emerging control design method which allows an engineer to systematically design an advanced controller for complex non-linear systems. As a result specific gain ranges can be determined which can prevent an operator (adversary) from accidentally (maliciously) setting control gains which could potentially destabilize the system. However in order to generate the controller the engineer will have to resort to using symbolic numerical solvers in order to complete the design. This can be both a cumbersome and error-prone task which can be automated. We present initial results of a tool which simplifies IDA-PBC. In addition many fluid control problems posses tight operating regions in which pumps degrade over time. As a result actuator saturation may occur for given set-point profiles which will lead to integrator wind-up and more oscillatory behavior. We provide a non-linear anti-windup control-law which greatly improves system resilience to such degradation. Finally we demonstrate that IDA-PBC works reasonably well for moderately large sampling times by simply applying the bilinear transform to approximate any additional (non-linear) integral control terms.

Service-Oriented Architectures (SOAs) are increasingly being used for designing and building large-scale networked and distributed systems. Catering to the complex and dynamically varying needs of business applications/clients, these systems must usually be realized by dynamically composing a variety of network-available services. Evaluation of large-scale SOAs, particularly on dynamic network platforms, such as Mobile Ad-hoc Networks (MANETs), is a non-trivial problem that requires not only a correct modeling of SOAs and the network platform, but also their relationships. This paper describes a new tool – SOAMANET – to design and rapidly synthesize simulations for the experimental evaluation of SOAs on MANET platforms. With its modeling techniques and analysis capabilities, SOAMANET allows simulationbased and system execution-based analysis of dynamic SOA and/or MANET designs and implementations.

Modern software-defined radios are large, expensive, and power-hungry devices and this, we argue, hampers their more widespread deployment and use, particularly in low-power, size-constrained application settings like mobile phones and sensor networks. To rectify this problem, we propose to put the software-defined radio on a diet by redesigning it around just two core chips – an integrated RF transceiver and a Flash-based, mixed-signal FPGA. Modern transceivers integrate almost all RF front-end functions while emerging FPGAs integrate nearly all of required signal conditioning and processing functions. And, unlike conventional FPGAs, Flash-based FPGAs offer sleep mode power draws measured in the microamps and startup times measured in the microseconds, both of which are critical for low-power operation. If our platform architecture vision is realized, it will be possible to hold a software-defined radio in the palm of one’s hand, build it for $100, and power it for days using the energy in a typical mobile phone battery. This will make software radios deployable in high densities and broadly accessible for research and education.

Our previous work has explored the use of compositional stabilization techniques for embedded flight control software[9] based on passivity properties of controller components and systems. Zames[21] presented a compositional behavior-bounding technique for evaluating stability of nonlinear systems based on real intervals representing cones (sectors) that bound possible component behaviors. Many innovations in control theory have developed from his insights. We present a novel use of his sector bound theory to validate the stability of embedded control implementations online. The sector analysis can be implemented as a computationally efficient check of stability for different parts of a control design. The advantage of the online application of this technique is that it takes into account software platform effects that impact stability, such as time delays, quantization, and data integrity. We present a brief overview of the sector concept, our compatible control design approach, application of the technique to model-based embedded control software design, an example of its use to find design defects, and insights that may be drawn from our investigation so far. In the present work we only consider software (discrete-time) control of nonlinear continuous-time systems without switching.

Understanding the aging mechanisms of electronic components in an avionics system is extremely important as they are part of the critical sub-systems avionics which includes the GPS and INAV systems. Electrolytic capacitors and MOSFET’s have higher failure rates than the other components in DC-DC power converter systems. With increased use of electronics in avionics system, it becomes very much important to understand these components degradation mechanisms and their effects on the rest of the system. Our current work focuses on analyzing and modeling degradation phenomena in electrolytic capacitors and its effects on the output of DC-DC converter systems. The output degradation is typically measured by the increase in ripple current and the drop in output voltage at the load. Typically the ripple current effects dominate, and they can have adverse effects on downstream components. For example, in avionics systems where the power supply drives a GPS unit, ripple currents can cause glitches in the GPS position and velocity output, and this may cause errors in the Inertial Navigation (INAV) system causing the aircraft to fly off course. Literature reports a number of operating conditions that may cause capacitor degradation. These include High Voltage conditions, Transients, Reverse Bias, Strong Vibrations and high ripple current. In our work, we have studied the effects of capacitor degradation on DC-DC converter performance by developing a combination of converter system model and a physics of failure model of electrolytic capacitor degradation when subjected to thermal and electrical stresses. Thermal stress occurs when the capacitors operate in high temperature environments, while electrical stress conditions occur due to high operating voltages and even ripple currents above the rated values. In our work we are developing models to capture the failure phenomenon in these components. In this paper, we discuss two experiments to observe degradation in electrolytic capacitors. In the first ageing experiment study, the capacitor was subjected to degradation for over 1000 hours of capacitor operation time under nominal room temperature conditions, and the degradation was monitored at regular intervals. In the accelerated ageing methodology study, the capacitors were subjected to high electrical stress. During the accelerated testing we observed a faster degradation in the capacitors where we measured the ESR (Equivalent Series Resistance) which increased over the period of time. We also discuss the future accelerated ageing method and tests for capacitor degradation. In this paper we present the details of our aging methodology along with details of experiments and analysis of the results

For many real-world systems, which exhibit complex, nonlinear, and hybrid behavior, it is important to accurately track and monitor the state and health of these systems. The continuous state estimation problem has been well studied, and a number of extensions of the Kalman filter to nonlinear systems have been proposed. Hy- brid state estimation poses an additional challenge, because the model must be quickly updated during a mode change to facilitate accurate, real time tracking. This paper discusses an approach to minimize the amount of equation regeneration necessary when the system undergoes hybrid mode changes. These equations are used as the state update equation for an Unscented Kalman Filter that tracks the system’s state. We demonstrate the effectiveness of our approach by tracking the hybrid behaviors of NASA’s ADAPT test bench. Results show that our algorithm scales well for tracking large nonlinear and hybrid systems.

The TrueTime toolbox simulates real-time control sys- tems, including platform-specific details like process scheduling, task execution and network communications. Analysis using these models provides insight into platform- induced timing effects, such as jitter and delay. For safety- critical applications, the Time-Triggered Architecture (TTA) has been shown to provide the necessary services to create robust, fault-tolerant control systems. Communication in- duced timing effects still need to be simulated and analyzed even for TTA-compliant models. The process of adapting time-invariant control system models, through the inclusion of platform specifics, into TTA-based TrueTime models re- quires significant manual effort and detailed knowledge of the desired platform’s execution semantics. In this paper, we present an extension of the Embedded Systems Model- ing Language (ESMoL) tool chain that automatically syn- thesizes TTA-based TrueTime models. In our tools, time- invariant Simulink models are imported into the ESMoL modeling environment where they are annotated with de- tails of the desired deployment platforms. A constraint- based offline scheduler then generates the static TTA execu- tion schedules. Finally, we synthesize new TrueTime models that encapsulate all of the TTA execution semantics. Using this approach it is possible to rapidly prototype, evaluate, and modify controller designs and their hardware platforms to better understand deployment induced performance and timing effects.

Computer science and computational engineering have enabled great advances in modeling and simulation to analyze various scenarios. Still, facilitating and enhancing situational awareness for a single human is rarely considered. Poor decisions by an individual encountering everyday challenges or public threat situations can have dramatic effects, both for the individual and others. In the presented research, a Computation of Things (CoTh) framework is proposed to provide individual decision support during crises and prevent long-term deviations from safe and secure conditions. The target of CoTh is to enable a profound understanding of the situation from the viewpoint of individual persons in order to permanently reduce their fear, while simultaneously increasing awareness of appropriate responses. CoTh allows for a quick forecasting of action (or non-action) alternatives based on an individual human context, including geographic position (e.g., pollution level and energy usage), activity patterns (e.g., personal nutrition habits, lifestyle, traveling load, family status, circle of friends, social network, and virtual life), and state patterns (e.g., the DNA, current health conditions, and musculature of a human), depending on the considered situation. Insights into CoTh's motivation, requirements, and challenges are provided and the architecture proposal is depicted.

Although traceability is often a suggested requirement for general software development, there are areas such as airborne systems, where traceability is a compulsory part of the development process. This paper describes a tool chain that is able to generate and to follow traceability links across model-to-model and model-to-code transformations, and capable of providing navigability support along these traceability links. We elaborate on the conceptual design of our tool chain and provide details on its realization in a DSML environment underpinned by graph rewriting-based model transformation.

The complexity of software in systems like aerospace vehicles has reached the point where new techniques are needed to ensure system dependability while improving the productivity of developers. One possible approach is to use precisely defined software execution platforms that (1) enable the system to be composed from separate components, (2) restrict component interactions and prevent fault propagation, and (3) whose compositional properties are well-known. In this paper we describe the initial steps towards building a platform that combines component-based software construction with hard real-time operating system services. Specifically, the paper discusses how the CORBA Component Model could be combined with the ARINC-653 platform services and the lessons learned from this experiment. The results point towards both extending the CCM as well as revising the ARINC-653.